Feed ii



Jan. 28, 1964 J. T. CABBAGE 3,119,764

METHOD OF REDUCING SULFUR CONTENT OF RESIDUAL PRODUCTS Filed June 1,1960 2 Sheets-Sheet 1 LIQUID DOWNFLOW OVERHEAD Ioo B/H PLUS IO B/H VAPORIo LB ORGANIC I I B/H SULFUR 4 437 LB SULFUR FRACTlONATOR-\ (I eooF FEEDII o 2| 2 22 I00 BIH ,1 I3 0 STEAM 420F U 4IOF 24 23\ 7o B/H 4IOFr--BOTTOMS 4.37 LB ORGANIC STRIPPING 90 am BOTTOMSN l7 STEAM ,4 SULFUR 5.63LB ORGANIC SULFUR F/G. FIG. 2

PRIoR ART PRIOR ART LIQUID DOWNFLOW LIQUIDIDOWNFLOW Ioo B/H PLUS I00 B/HPLUS 10 LB ORGANIC IO LB ORGANIC VAPOR VAPOR Io B/H SULFUR lo BIH SULFUR7.0 L8 SULFUR 7.0 L8 SULFUR FRACTIONATOR FRACTIONATOR 1.. \J In 0 8 600F I 34 PARTITION ,x STEAM 33 32 STEAM E 2 600 F 70 B/H 39H" 4|oF 56 4|oF7 LB ORGANIC SULFUR 36 4o 57 7o B/H 7.0 LB ORGANIC I BOTTOMS FIG 4SULFUR 3 LB OQISL'SIIC SULFUR I BOTTOMS 9o B/H 3 LB ORGANIC SULFURINVENTOR- J.T. CABBAGE BY F/G. 3 5

A TTORNEYS Jan. 28, 1964 J. T. CABBAGE METHOD OF REDUCING SULFUR CONTENTOF RESIDUAL PRODUCTS Filed June 1, 1960 I00 B/H l0 LB ORGANIC VAPORSULFUR 2 Sheets-Sheet 2 70 B/H 7L5 ORGANIC SULFUR 7O VENT 9o BIHJ STEAM68 FIG. 5

STEAM STRIPPER 90 B/H 3L5 ORGANIC] SULFUR IN VEN TOR.

:J.T. CABBAGE A 7' TORNEYS PntenteHJan. 28, 1964 United States PatentOffice 3,119,764 METHOD OF REDUCING SULFUR CONTENT OF RESIDUAL PRODUCTSJohn T. Cabbage, Bartlesville, Okla., assignor to Phillips PetroleumCompany, a corporation of Delaware Filed June 1, 1960, Ser. No. 33,156 5Claims. (Cl. 208-208) This invention relates to the reduction of thesulfur content of an oil. In one aspect, the invention relates to theheat treating of a sulfur compound containing oil. In another apect, theinvention relates to the reduction of the sulfur content of a product ofa distillation column. In another aspect, the invention relates to thereduction of the sulfur content of a product of a fractionator. In stillanother aspect, the invention relates to thermal desulfurization of thebottoms yield of a fractionator. In another aspect, the inventionrelates to the reduction of the content of sulfur compounds in residualproducts by reboiling the' bottoms of the fractionator and introducingstripping steam. In a further aspect, the invention relates to thefractionation of crude oil wherein the residual product is subjected toan elevated temperature to reduce the sulfur content of the product. Inanother aspect, the invention relates to the control of the feed to thereboiler by withdrawing the feed directly from the bottom tray downcomerof the fractionator. In another aspect, the invention relates to thecontrol of the feed to the reboiler by utilizing a partitioned bottom ina fractionator. In still another aspect, the invention relates to thereduction of the sulfur content of the product of a distillation columnby controlling the feed to the reboiler in such a manner that the heattreated material cannot recycled back through the reboiler.

Reduction of the sulfur content of a residual oil is definitely requiredwhen the oil is used as is, or is blended into fuel oil if, withoutsulfur reduction, the fuel oil cannot meet the sulfur specification.Further, where residual oil, such as topped crude, is to be processed ina vacuum unit, the heat treatment in the distillation operation willbreak out a major portion of the reactive sulfur and thereby reduce theload on the vacuum jets in the vacuum flasher (resulting in a saving ofinvestment cost and operating expenses of a vacuum operation).

Sulfur compounds in crude oil are usually made up of a number ofdifferent organic sulfur compounds which vary in thermal stability. Forexample, a portion of the sulfur compounds will decompose rapidly at 400F., and other portions can react very slowly. If the reactiontemperature is raised to 500 F. then an additional fraction can reactrapidly, while the remainder of the sulfur compounds are relativelystable at thistemperature. When the reaction temperature is raised to600 F., a furtheradditional fraction can react rapidly, leaving asubstantially smaller amount, if any, of stable sulfur compounds. v

In the distillation of oils, a product can be desulfurized by subjectingthe oil to an elevated temperature to crack or destroy at least aportion of the sulfur compounds therein. The heat treatment of the oilproduces hydrogen sulfide in vapor form which can be removed from theoil by steam stripping. I have found that a sub stantial gain in theeffectiveness of utilizing a heat treatment to desulfurize the oil canbe made by maintaining the portion of the treating zone from which thesulfur compound containing oil is withdrawn for heating, sub

a portion of the oil from a first section of the fractionator, heatingthe removed oil to a temperature at which sulfur compounds therein willdecompose, thus decomposing sulfur compounds therein, returning the thustreated oil to a second section of said fractionator separate from saidfirst section and withdrawing from said second section directly and fromthe operation as a product thereof oil in said second section, ascontrasted with withdrawing a portion of the product stream, heattreating said product stream portion and introducing said product streamportion back into the bottom of the fractionator. The latter operationallows a part of the treated portion to be recycled again through theheat treating means thus reducing the amount of fresh material which canbe heat treated.

Accordingly, an object of this invention is to desulfurize an oil.Another object of this invention is to desulfurize a product from adistillation column. Still another object of this invention is todesillfurize a product from a fractionator. Still another object of thisinvention is to desulfurize the residual product of a fractionator.Another object of this invention is to provide a method for increasingthe destruction of organic sulfur compounds in a bottoms product from afractionator. Another object of this invention is to provide a methodand/or an apparatus for more complete removal of organic sulfurcompounds from the topped crude. A further object of this invention isto provide a method of and means for desulfurization of topped crudewhich will result in material savings in the investment cost andmaintenance expenses of the equipment for processing topped crude in avacuum flasher operation. Another object of this invention is to reducethe load on the vacuum jets in a vacuum flasher by providing an improvedmethod of desulfurizing the residual oil prior to its treatment in avacuum flasher. Another object of this invention is to reduce the sulfurcontent of fuel oil.

Other aspects, objects, and the several advantages of the invention areapparent from a study of the disclosure, the drawing, and the appendedclaims.

According to this invention, there are provided a method and means fortreating a sulfur compound containing oil wherein the oil is removed,from a treating zone in which vaporization can occur and heated to causedecomposition of said sulfur compound and returned to said treating zonefor further treatment therein, and the portion of the treating zone fromwhich the sulfur com- .pound containing oil is withdrawn for heating ismaintained substantially free from any returned oil which has been heattreated to decompose sulfur compounds therein,,which does not vaporizein said treating zone.

In the drawing, FIGURE 1 is a diagrammatic view of one conventionalmethod of fractionating crude oil by supplying heat to fractionation aspreheat. FIGURE 2 is a diagrammatic view of another conventional methodwherein the heat is supplied by reboiling. FIGURE 3 is a diagrammaticview of a flow arrangement for carrying out the present invention.FIGURE 4 is a diagrammatic view of another flow arrangement for carryingout the present invention. FIGURE 5 is a diagrammatic view as stillanother flow arrangement for carrying out the present invention.

In FIGURE 1, crude 'oil is fed to pipe 11 to a preheater 12 and thenthrough pipe 13 to fractionator 14. Stripping steam is introduced intofractionator 14 by pipe 15. Overhead vapors are removed through pipe 16while the bottoms product is removed through pipe 17. The temperature ofthe oil in pipe 11 may be 300 F., the temperature of the oil in pipe 13may be 420' F., and the bottoms product may be approximately 410 F.

In FIGURE 2, the downflowing fluid in the fractionator 20 collects in abottom trap-out tray 21 and then overflows into the bottom compartment22 of the fractionator. The bottoms product is removed from fractionator20 by pipe 23. A portion of the bottoms product is taken from pipe 23through pipe 24 to reboiler 25 where the temperature of the bottomsproduct is raised from approximately 410 F. to approximately 600 F. andthen returned to bottom compartment 22 of fractionator 20 by pipe 26.Stripping steam is injected into compartment 22 by pipe 27. This is aconventional arrangement whereby heat for the organic sulfur destructionis supplied by reboiling. This operation results in greater organicsulfur destruction than the method ofFlGURE 1, due to the higher oiltemperature (410 to 600 in FIGURE 2 as contrasted with 300 to 420 F. ofFIGURE 1). The arrangement of FIGURE 2 allows much of the organic sulfurto bypass the reboiler, thus decreasing the effectiveness of thisarrangement for desulfurizing a residual oil. It should be noted that alarge part of the material which is cycled through reboiler 25 andreturned to fractionator 20 and then removed through pipe 23 may againreturn to reboiler 25. This continual recycling of a portion of thefluid decreases the amount of fresh fluid which may be treated in thereboiler, thus decreasing the effectiveness of the reboiler fordesulfurizing the residual product.

My invention, illustrated in FIGURES 3, 4, and 5, rearranges thereboiler suction locus to maximize the organic sulfur going to thereboiler, which increases the organic sulfur destruction.

In FIGURE 3, the downflowing fluid in fractionator 30 collects in thebottom trap-out tray 31 and then overflows into compartment 32. Thebottom of fractionator 30 is separated into two compartments, 32 and 33,by the vertical partition 34. A portion of the bottoms product isremoved from compartment 32 by pipe 35 and transmitted to reboiler 36where the temperature of said portion of bottoms product is increasedfrom approximately 410 F. to approximately 600 F. Said portion of thebottoms product is passed from reboiler 36 to compartment 33 by pipe 37.The partition 34 is spaced from the lower most plate 38 of fractionator30 to permit the excess fluid in compartment 32 to flow over partition34 into compartment 33. Stripping steam is injected into compartment 33through pipe 39. A final bottoms product is removed from compartment 33by pipe 40.

In FIGURE 4, the downflowing fluid in fractionator 50 collects in thebottom trap-out tray 51. the downflowing fluid is removed from tray 51by pipe 52 and is transmitted to and through reboiler 53, where thetemperature of said portion is raised from approximately 410 F. toapproximately 600 F. and then said portion is returned by pipe 54 tobottom compartment 55 of fractionator 50. Stripping steam is injectedinto compartment 55 through pipe 56. The bottoms product is removed fromcompartment 55 by pipe 57.

In FIGURE 5, the downflowing fluid in fractionator 60 collects in thebottom trap-out tray 61. A portion of the downflowing fluid is removedfrom tray 61 through pipe 62 and transmitted to and through reboiler 63where the temperature of said portion is raised from approximately 410F. to approximately 600 F. and then said portion is returned by pipe 64to bottom compartment 65 of fractionator 60. The bottoms product isremoved from fractionator 60 through pipe 66 and injected into steamstripper 67. Stripping steam is fed into steam stripper 67 by pipe 68.The vapors are removed from stripper 67 by pipe 69 and then eithervented through pipe 70 or returned to bottom compartment 65 by pipe 71.This may be accomplished by venting all of the vapors or transmittingall of the vapors to fractionator 60, or by venting part of the vaporsand transmitting the remainder of the vapors to fractionator 60. Theresidue from the steam stripping operation is removed from stripper 67through pipe 72.

A portion of For purposes of illustration and not in limitation of theinvention, it can be seen that when ten pounds of organic sulfur perbarrels of material enters the bottom of the tower as downflow, and theorganic sulfides are destroyed at reboiler temperatures, that in FIG-URE 2, the ten pounds of organic sulfur entering with the 100 barrelsmixes with 60 barrels of liquid returned from the reboiler resulting inbarrels containing ten pounds of organic sulfur. This results in 0.0625pound of organic sulfur per barrel. Organic sulfur charged to thereboiler is 70x0.0625 or 4.37 pounds. Assuming for comparison that nodestruction occurs in the bottom of the tower, the remainder, 5.63pounds, yields unconverted with the bottoms product.

In FIGURES, the 70 barrels of reboiler charge is drawn directly from thedowncomer which contains 0.1 pound organic sulfur per barrel. Thus, 7pounds of organic sulfur are charged to the reboiler, leaving but 3pounds yielded with the bottoms.

It is to be understood that the arrangement in FIGURE 4 gives the sameresults as FIGURE 3 except that FIG- URE 4 permits more reaction time inthe bottom of the tower (wherein additional destruction can occur).

It is also to be understood that the arrangement in FIGURE 5 can be usedto give adequate stripping of hydrogen sulfide formed from the bottomsproduct. This stripping can be done in two towers as shown or in asingle tower where the reboiler charge is withdrawn a few trays up fromthe bottom.

The use of a pump to charge the reboiler and a back pressure controlvalve to increase time and temperature in the coil at the same heat tothe tower is known in the prior art.

The temperatures given in the description of the drawing are forpurposes of illustration. The particular temperature of the lowersection of a fractionator is determined by the composition of the feedto the fractionator and the desired fractionating conditions, such asthe desired composition of the overhead products.

As noted above, the drawing is merely diagrammatic and is not intendedto fully show all component parts of equipment which one skilled in theart will routinely design for the operation. Indeed, the showing of anelement or piece of equipment does not mean that all such or similarpieces of equipment which may or can be designed by one skilled in theart in possession of this disclosure cannot be utilized in substitutiontherefor,

Tabulation Figure and Stream Va r Organic p0 Sulfur Figure 2:

Downflow to 21 To Reboil 24 From Reboii 26 Vapor Bottoms Yield ure 3:

Downflow to 31 To Reboil 36 From Reboil 37 Linniri Fig Vapor BottomsYield Figure 4' Downflow to .5l

To Reboil 52 From Reboii 54.

Linnirl Vapor Bottoms Yield Figure 5:

Downflow to 61 To Reboil 62 Fret}: Reboil 64.-

Vapor Bottoms Yield...

1 H18 reported as sulfur, and returning all vapors via 71 in Figure 5.

likewise the omission of an element which one skilled in the art mayinclude in an actual unit does not mean that such a piece of equipmentis intended to be omitted simply because it does not appear in thedrawing. Suffice to say, the drawing is for illustrative purposes as isthe description thereof.

All data arebased on 100 b./h. topped crude charge (Western Kansascrude) containing 0.1 barrel organic sulfur compounds (measured assulfur). All fractionations are operated under like. conditionsincluding bottom tower temperature of 410 F., and reboiler efliuent of600 F. with 100 percent destruction of organic sulfur compounds. Eachexample yields vapor from the bottom zone equivalent to liquid b./h. Thesame quantities of stripping steam are used in all examples. Eachexample yields 90 b./h. of bottoms product. It is seen that whenoperating in accordance with my invention, as compared to prior artpractice, the bottoms products from my processing contain only 53percent as much organic sulfur as the bototms produced conventionally.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure, the draw ing, and the appended claims to theinvention the essence of which is that a sulfur compound containing feedfrom a distilling or other treating zone to a heating zone is taken froma section of said distilling or treating zone which is maintainedsubstantially free from any returned oil which has been heat treated todecompose sulfur compounds contained therein which does not vaporize insaid distilling or treating zone.

I claim:

1. A method of reducing the sulfur content in a bottoms product from afractionation column, said fractionation column having a first sectionand a second section with vapor phase communication therebetween,comprising the steps of withdrawing a portion of liquid thereincontained from said first section and from said fractionation column,heating the thus withdrawn portion to a temperature at which sulfurcompounds therein will decompose, thus decomposing sulfur compoundscontained therein; passing the thus'heated portion into said secondsection, maintaining said first section substantially free of any ofsaid portion which has been heat treated to decompose sulfur compoundscontained therein and which did not vaporize during the step of heating,withdrawing at least a portion of the thus decomposed sulfur compoundsfrom the top of said fractionation column, and withdrawing from thebottom of said fractionation column a bottoms product having asubstantial reduction in the concentration of sulfur compounds containedtherein.

2. A method of reducing the sulfur content in a bottoms product from afractionation column, said fractionation column having an upper section,a bottom section and a trap-out tray positioned within saidfractionation column and between said bottom section and said uppersection, said bottom section being in vapor phase communication withsaid upper section, comprising the steps of withdrawing a portion ofdownfiowing fluid therein contained from said trap-out tray and fromsaid fractionation column; heating the thus withdrawn portion to atemperature at which sulfur compounds therein will decompose, thusdecomposing sulfur compounds contained therein; passing the thus heatedportion into said bottom section; withdrawing a bottoms product fromsaid bottom section and from said fractionation column, and withdrawingat least a portion of the thus decomposed sulfur compounds from saidupper section.

3. A method of reducing the sulfur content in a bottoms product from afractionation column, said frac- 6 tionation column having an uppersection, a bottom section and a trap-out tray positioned within saidfractionation column and between said bottom section and said uppersection, said bottom section and said upper section being in vapor phasecommunication, comprising the steps of withdrawing a portion ofdownflowing fluid therein contained from said trap-out tray and fromsaid fractionation column; heating the thus withdrawn portion to atemperature at which sulfur compounds therein will decompose, thusdecomposing sulfur compounds contained therein; passing the thus heatedportion into said bottom section; injecting stripping steam into theliquid in said bottom section; withdrawing a bottoms product from saidbottom section and from said fractionation column, and withdrawing atleast a portion of the thus decomposed sulfur compounds from said uppersection and from said fractionation column.

4. A method of reducing the sulfur content in a bottoms product from afractionation column, said fractionation column having an upper section,a bottom section and a trap-out tray positioned within saidfractionation column and between said bottom section and said uppersection, said bottom section and said upper section being in vapor phasecommunication, comprising the steps of withdrawing a portion ofdownflowing fluid therein contained from said trap-out tray and fromsaid fractionation column; heating the thus withdrawn portion to atemperature at which sulfur compounds therein will decompose, thusdecomposing sulfur compounds contained therein; passing the thus heatedportion into said bottom section; withdrawing a bottoms product fromsaid bottoms section and from said fractionation column, steam strippingthe thus withdrawn bottoms product, and withdrawing an overhead productfrom said upper section and from said fractionation column, saidoverhead product containing at least a portion of the thus decomposedsulfur compounds.

of withdrawing a portion 5. A- method of reducing the sulfur content ina bottoms product from a fractionation column, said fractionation columnhaving a bottom section, a partition positioned in said bottom sectionand dividing said bottom section into a firstcompartment and a secondcompartment, and a trap-out tray positioned within said fractionationcolumn and above said bottom section so that downflowing liquidoverflows from said trap-out tray into said first compartment, saidsecond compartment beingv in vapor phase communication with the upperportion of said fractionation column, comprising the steps ofliquidtherein contained from said first compartment, heating the thuswithdrawn portion to a temperature at which sulfur compounds thereinwill decompose, thus decomposing sulfur compounds contained therein;passing the thus heated portion into said second compartment; injectingsteam into the liquid in said second compartment, withdrawing a bottomsproduct from said second compartment and from said fractionation column,and withdrawing from the top of said fractionation column an overheadstream containing at least a portion of the thus decomposed sulfurcompounds.

References Cited in the file of this patent UNITED STATES PATENTS Canada

1. A METHOD OF REDUCING THE SULFUR CONTENT IN A BOTTOMS PRODUCT FROM AFRACTIONATION COLUMN, SAID FRACTIONATION COLUMN HAVING A FIRST SECTIONAND A SECOND SECTION WITH VAPOR PHASE COMMUNICATION THEREBETWEEN,COMPRISING THE STEPS OF WITHDRAWING A PORTION OF LIQUID THEREINCONTAINED FROM SAID FIRST SECTION AND FROM SAID FRACTIONATION COLUMN,HEATING THE THUS WITHDRAWN PORTION TO A TEMPERATURE AT WHICH SULFURCOMPOUNDS THEREIN WILL DECOMPOSE, THUS DECMPOSING SULFUR COMPOUNDSCONTAINED THEREIN; PASSING THE THUS HEATED PORTION INTO SAID SECONDSECTION, MAINTAINING SAID FIRST SECTION SUBSTANTIALLY